Emacs' TRAMP feature (Transparent Remote file Access, Multiple Protocol) is an extremely powerful tool for editing files that exist on remote systems, or require access using a different user account from your main Emacs session, or both.

Some of the things that TRAMP can do include:

Editing files on a remote development server over SSH (e.g. /ssh:remote-user@remote.box:/path/to/my/file)